Spacetime singularties are often taken to be either a location in space or an event in time at which general relativity is no longer applicable. Physically this is often associated with the curvature of spacetime -- hence gravity -- becoming unbounded. Sir Roger Penrose was awarded the Nobel prize in 2020 for his proof of the singularity theorem. The theorem states that once a closed trapped surface is formed under gravitational collapse, then a spacetime singularity must form in a finite time (see illustration below). Penrose realized that if naked singularities (that is, singularities that are not hidden behind the black hole horizon) exist, this would be problematic for the theory of general relativity. Such singularities could render the theory rather useless as initial conditions can no longer be solved to tell us a system evolves in time under the influence of gravity, since signals from the unknown physics of singularities would affect them. For this reason Penrose proposed the "cosmic censorship conjecture", which states that under generic conditions naked singularities cannot be formed.

On August 23, 2021, Scientific American published an article titled "Singularities Can Exist Outside Black Holes -- in Other Universes". The article disccused the current status of the frontier research in cosmic censorship, namely there are some known counter-examples to the conjecture, so it remains to be seen under which conditions the conjecture is true. In fact, nowadays some physicists view the violation of cosmic censorship as a welcomed opportunity, as signals coming from the singularities could provide hints about quantum gravity that we so desperately need. In addition, the nature of singularity, and whether it can indeed be "cured" by quantum gravity, also remains unanswered. 

Prof. Yen Chin Ong was invited for an interview by the author Brendan Z. Foster, after the latter read Prof. Ong's review article "Spacetime Singularities and Cosmic Censorship Conjecture: A Review with Some Thoughts" published in Int. J. Mod. Phys. A (the preprint is available at arXiv:2005.07032 [gr-qc]). There are still plenty of interesting questions to be solved regarding singularities, and as Prof. Ong concluded in the interview, the strict validity of the conjecture itself is no longer the main point for most theorist, "it is what we can learn along the way, what insights we can gain, what tools we can develop along the way. The journey will be important, not just the destination."

It is worth mentioning that Prof. Ong was also invited to present at the international meeting "Singularity theorems, causality, and all that: A tribute to Roger Penrose" held online from June 14 to June 18, 2021. Speakers were by invitation only. In this meeting, Prof. Ong gave a talk titled "Cosmic Censorship from the Quantum Perspective", in which he conjectured that cosmic censorship remains relevant even in quantum gravity, and that quantum information might lead to a deeper understanding of singularities.